It makes sense to me that he would only disperse information to people he trusts. You can't just give everyone techniques since you don't know who the actual traitors are. So him being tight lipped about what to teach whom makes sense. Also as for the older generational people that he trusts, there's also the issue of gaining their trust so that he can give them the techniques that he knows. Do you think Yo Zhong would have trusted him before the poison incident? Probably not.
As for making "everyone wealthy" remember they are in a closed economy. You can't make everyone rich in that situation, you can only make yourself rich. The city lord is already rich. The orchard society is rich as well. There would be no point in him enriching those groups. He can (and did) help his friends make money, but that only works if only a select group of people have the knowledge of what is being done. Otherwise, if it's common knowledge, it won't hold any value and can't be sold. For example the purple grass that could only be stockpiled while people didn't know it's use.